I have two ULS-15s and HB-1 Mk.2s that I run in stereo. Up to now I used the crossover in the ULS-15s and let the HB-1s shift for themselves. However, I don't have any room treatment at all and a few weeks ago I was trying to even out my room. I discovered, although I was crossing over the ULS-15s at 80Hz, the HB-1s were producing full output all the way down to 40Hz. I don't think they are supposed to but I guess the room favors it. Anyhow, I decided to do something about it.

I use Pure Music and Pure Vinyl which support a 64bit electronic crossover system that can handle up to four independent output channels per side. I suppose, if you could do it, you could have a SW, W, M and T. I just have the SW and M/T. No problem.

I just got this thing wired up yesterday and haven't done any fine-tuning whatsoever. However, using an 80Hz crossover at 24 db/octave, I am already amazed at how much better it sounds. I know the HB-1s are supposed to roll-off naturally and don't actually require a crossover but adding one really makes the higher frequencies so much cleaner. This is probably wrong but it seems pushing the HB-1s below 80Hz adversely affects their ability to handle the higher frequencies cleanly.

This stuff is sort of mentioned in the manuals but it isn't pushed the way it should be. I wouldn't have considered it if I hadn't decided to check my room's response to each speaker. Hsu sells a high-pass filter which you ought to use if you have no other way to do it.

[Edit] There is one negative. Lousy recordings sound REALLY lousy. This is a very revealing setup.

Excellent review. We do recommend using a high pass filter/crossover at 80 Hz for the speakers whenever possible. I wouldn't say that setting a crossover will necessarily help the high frequencies but, it would definitely improve things on the mid-range driver for sure. Also, it would help free up the clean headroom of your amp because low bass frequencies require quite a lot of power to drive. So putting in a high pass filter on the mains will help give you better dynamic range/clean output. That might explain why you hear better cleanliness overall.

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